Rete engines, which are very efficient software tools to process rules, have been known to those skilled in the art since 1982. Currently three major competitors in this field are known to the inventor. Two are commercial providers of rule engines that are usually used for configuration applications. Another is an open source type of engine.
To make a Rete or rules engine useful, it must be somehow integrated into an application. For example, when designing an automobile for sale, a designer can select from a wide variety of options and combinations of options. If, for example, a car has a two-liter engine, it cannot have both power windows and air conditioning, because both systems being used together would exceed the electrical power available from a two-liter engine. However, both systems may be included in the design if the car has a three-liter engine. When an automobile is being designed, these and a multitude of other, similar rules must be observed to ensure that the features included in any one combination of options conform to all the limitations inherent in its design.
Another example of using rules is in banking, where customer transactions, for example, are governed by a variety of combinations of rules. For example, certain customers cannot do certain transactions unless certain documents are on file with the bank. Or, in another example, taxes may be withheld on distributions of income from investments if no exemptions from withholding are on record in the bank. In every case, each transaction must be checked against several or all of the rules to ensure that all the laws that have been converted into rules have been obeyed in performing these transactions.